The present invention relates to a steerable nozzle for a reaction engine, i.e. a nozzle which is capable of steering the jet from a reaction engine. More particularly, the present invention relates to a nozzle having a fixed portion with steerable flaps hinged thereto. When mounted on an airplane, such a nozzle enables the pilot to vary the pitch and the yaw of the airplane rapidly (and indeed the roll for a two-engined airplane).
Nozzles of this type are known in the art. Some make use of an activation ring disposed at a downstream end of the fixed portion and connected to the flaps. The activation ring is moved by means of actuators, thereby steering the flaps. Such nozzles require complicated equipment, in particular universal joints, for transmitting displacements from the activation ring to the flaps.
The present invention seeks to provide a nozzle with steerable flaps having a structure that is simpler and less expensive.
To this end, the invention provides a steerable nozzle for a reaction engine, the nozzle comprising a fixed portion for attaching to the engine, a plurality of steerable flaps mounted on one end of the fixed portion, and means for steering the flaps, the nozzle being characterized in that the flap steering means comprise: a resilient ring having a first circumference secured to said end of the fixed portion and a second circumference connected to the flaps; and control means enabling the second circumference of the resilient ring to be moved relative to the first circumference.
The resilient ring of the invention serves firstly to activate the flaps under drive from control means, and secondly to take up the reaction forces. In addition, because of the annular structure of the actuator system constituted by the resilient ring, the equilibrium position of the nozzle corresponds to the rest position of the ring, thereby providing additional safety in the event of the control means breaking down.
The resilient ring can be continuous or in sectors. In addition, and typically, said first and second circumferences of the resilient ring are respectively the inner circumference and the outer circumference thereof.
The resilient ring is preferably made of a laminated material constituted by a stack of alternating layers of elastomer and of metal, a stack of alternating layers of elastomer and an organic composite material, or a stack of alternating layers of elastomer and of a thermostructural material. The elastomer is selected from elastomers capable of withstanding temperatures greater than 150xc2x0 C. By way of example, an elastomer is used that is selected from fluorocarbon and fluorosilicone materials, and from hydrogenated elastomers such as hydrogenated nitrile butadiene rubber (HNBR).
Advantageously, the first circumference of the resilient ring is formed by a first rigid annular hoop serving as a fixed support to the resilient ring that is secured to the fixed portion of the nozzle, and the second circumference of the resilient ring is formed by a second rigid annular hoop serving as a moving support for the resilient ring that is connected to the control means and to the flaps. The structure formed by the resilient ring and the two rigid annular hoops constitutes a single piece, thereby minimizing operating clearances and the number of moving parts.
The control means moves the second circumference of the resilient ring directly, which movement steers the flaps.
In a first embodiment of the invention, the control means comprises first actuators of the hydraulic or electrical type, placed on the circumference of the fixed portion of the nozzle. The second rigid annular hoop has first fixing tabs to which the free ends of the first actuators are fixed, and second fixing tabs to which panels or connecting rods are attached. The flaps are hinged at first respective locations to said panels or connecting rods, and at second respective locations to the fixed portion of the nozzle.
In another embodiment of the present invention:
said flaps are controlled diverging flaps;
the nozzle also has controlled converging flaps;
the second rigid hoop has second fixing tabs to which the panels or the connecting rods are attached;
each controlled diverging flap is hinged at a first location to a panel or a connecting rod, and at a second location to a controlled converging flap; and
the controlled converging flaps are also hinged to the fixed portion.
Means are then provided to steer the controlled converging flaps. These means which enable the diameter of the throat of the nozzle to be modified, i.e. the diameter of the cross-section defined by the hinged points between the converging and diverging flaps, can comprise second actuators disposed on the circumference of the fixed portion, a ring substantially perpendicular to the longitudinal axis of the nozzle and to which the free ends of the second actuators are connected, and wheels mounted in said ring, each following a cam surface on a controlled converging flap.
Advantageously, this embodiment further comprises antirotation means to restrict rotary movements of said ring about the longitudinal axis of the nozzle. The antirotation means comprise said second actuators fitted with side links each hinged at a first end to the cylinder of the corresponding actuator and at a second end to the fixed portion.
The nozzle of the invention can also have following diverging flaps and following converging flaps interposed respectively between the controlled diverging flaps and the controlled converging flaps.